Plunger sealing means for microliter burette



Feb. 18, 1964 M. c. SANZ PLUNGER SEALING MEANS FOR MICROLITER BURETTE Filed April 18, 1961 2 Sheets-Sheet I1 mil/1114911011 74 F II 5 E IN VENTOR. l'fmmsg. Smvz Feb. 18, 1964 M. c. SANZ 3,121,513

PLUNGER SEALING MEANS FOR MICROLITER BURETTE Filed April 18, 1961 2 Sheets-Sheet 2 FIG.7

INV ENT OR. Ham/cl t1 51/12 jzuq/ 3,121,513 Patented Feb. 18, 1964 3 121,513 PLUNGER SEALING MEAN FOR MECROLITER BURETTE Manuel Claude danz, 46 Ave. Tournay, tjhamhesey, Geneva, Switzerland Filed Apr. 18, 1% Ser. No. 163,897 2 Claims. (fill. 222-45) The present invention relates generally to a burette and more particularly to a microliter burette capable of supplying an indication of predetermined and variable small quantities of delivered liquid.

This application is a continuation-in-part of US. application Serial No. 689,806, filed October 14, 1957 now abandoned in favor of this application and application Serial No. 103,896, filed April 8, 1961, now Patent No. 3,040,931.

Among the objects of the invention is to provide a burette capable of delivering predetermined small quantitles of liquid and indicating exactly the quantities delivered.

Among other objects of the invention is to provide a urette capable of delivering small quantities of liquid and indicating the quantity, and in which the indicator may be reset to zero at the termination of delivery of each sample thereby simplifying the successive readings.

.lt is a further object of the invention to provide a burette with a mechanical means to precisely meter liquid from a chamber and record the amount of liquid metered in which the burette includes means to prevent leakage of the liquid from the chamber back into the recording means.

These and other objects of the invention will become more clearly apparent from the following description when taken in conjunction with the accompanying drawing.

Referring to the drawing:

FIGURE 1 is a side elevational view, partly in section, of a burette constructed in accordance with the invention;

FIGURE 2 is a schematic view indicating a particular arrangement of the indicator mechanism;

FIGURE 3 shows the frictional attachment of the pointer to the drive shaft;

FEGURE 4 shows a suitable reset mechanism; and

FIGURE 5 is an enlarged view, in section, showing the attachment of the sample rod to the drive.

FIGURE 6 is a rear view, partly broken away (and with a plate removed), of a modified form of the invcntion.

FIGURE 7 is a greatly enlarged detail View of the sealed portion of FIG. 6.

ln general, the burette employs a micrometer movement including a micrometer nut and screw to advance a rod into a reservoir containing a liquid sample. The rod displaces the liquid sample as it is advanced into the reservoir. The micrometer screw advances the rod a predetermined distance into the reservoir for each revolution to displace an exact amount of liquid. Suitable indicator means are associated with the apparatus for accurate-1y indicating the rotative movement of the micrometer screw and give an indication of the advance of the rod into the sample reservoir. In FlGS. 1-5, such means includes a wire or other suitable filamentary material which, winds onto the rotating rod and which has its free end spring loaded. The wire is wound around an element which drives a pointer to indicate the linear dis placement of the wire.

Referring more particularly to FIGURE 1, a micrometer movement 11 having a knob 12 which rotates the screw (not shown) to advance the rod 13 is shown. The knob 12 rotates about the barrel 14 which is adapted to hold the not of the micrometer movement. The end portion of the barrel 14 is adapted to receive the tube 16. The rod 13 extends coaxially within the tube 16. Suitable means are provided for receiving and holding the end portion of the wire 18. For example, the end may be held by the screw 17. The wire is then wound onto the rod and extends upwardly through the opening 2% formed in the tube into the indicator 2 1, to be presently described in detail.

Referring particularly to FIGURE 5, a glass, synthetic material, or the like, inert rod 22 is suitably attached to a metallic pin 23 as, for example, by accommodating the end Within the hole 24 formed in the member 23. The member 23 is held by a cup-shaped element 25 which is suitably secured to the adjacent end of the micrometer rod 13, as for example, by means o f set screws 1.7. Thus, while the micrometer rod 13 is rotated, the rod 22 and member 23 are moved axially but are not adapted to rotate therewith.

The forward end of the rod 22 extends into the liquid sample reservoir 26 through a suitable packing means. For example, the packing means may include a cumshaped member 27 which may be formed 05% hard inert material, for example, Teflon or Kel-F, which rides tightly over the rod 23. A packing ring 28 of softer material like silicon rubber is placed within the member 27. When compressed, the material 28 forms a packing which prevents leakage of sample liquid from the reservoir into the tube 15. The liquid reservoir 26 which may be formed of glass has a cup-shaped Teflon sleeve 29 suitably secured thereto as, for example, with epoxy cement. The reservoir is mounted on the apparatus by sliding the slwve 29 over the rod 22 until it abuts against the pack ing 28. A suitable cap 3% is then secured as, for example, by threads to the adjacent portion of the tube 316. When the cap is tightened, the packing 28 bears tightly against the rod 22 to form the seal, previously described.

The amount of axial movement of the micrometer rod 13 and, consequently, the rod 22 may be obtained by a reading of the micrometer dials. Iowever, repeated readings are relatively inaccurate and ditficult to make when small rotative movement is required. Consequently, a novel indicating means is associated with the rod 13 to give an expanded reading which is considerably easier to read than one which might be obtained oy reading of the micrometer dials. The wire 13 which winds onto the rod 13, passes upwardly into the indicator 2i and makes a one or two-turn loop over the pulley 31 which is carried on the shaft 32 which drives a pointer 33 (FIGURE 1). The wire 18 then extends upwardly and is reeled onto a suitable pulley 34. The pulley 34 is geared to a spring means 35 which may, for exam le, be a spring of the type used for the main spring of a watch or the like. The spring means 35 serves to maintain a relatively constant tension on the wire 18 whereby the same frictionally engages the pulley 3i and winds spirally and tightly onto the rod 13. As the rod rotates, the wire 18 is spirally wound thereon and is moved downwardly thereby rota-ting the pulley 31 and shaft 32 which, in turn, moves the pointer 33 of the indicating means. By suitably choosing the ratio or diameter of the rod 13 and pulley 31, an expanded reading may be obtained. For example, if the two have the same diameter, then one turn of the rod 13 will give a complete revolution of the pointer 33. This is a relatively large expansion of the rotativc movement of the rod and easily read in comparison with a reading from the micrometer dials.

It may be desirable to obtain a count of the revolutions when large quantities of liquids are dispensed. Consequently, a suitable gear is carried by the shaft 32 to drive a revolution counter indicator 36. Referring to FIG- URE 2, for example, the gearing may include an idler gear 37 and a gear 38 which has its shaft 32 suitably secured to the dial 36 to thereby drive the same. Any ratio of turns between these dials may be obtained by suitably choosing the ratio of diameters of the various gears forming the gear drive or by adding more gears.

The wire or filamentary material 18 may be made of steel, or synthetic material, for example, nylon, or silk or the like. Preferably, the filamentary member 18 should be of such material that it does not stretch with moisture or temperature changes. It must be strong enough to withstand the tension applied to the same. The various packing means and reservoir 26 which are in contact with the liquid to be measured should be made of material that is not attacked by the liquid.

[it is apparent that it is desirable to be able to reset the dial to zero at the completion of delivering each sample thereby eliminating the necessity of subtracting one reading from another. Such means might comprise a reset mechanism. The reset mechanism might include a push button 41 which extends outwardly from the side of the dial indicator and which controls a reset mechanism. The button 41 might, for example, urge the end 42 of the reset lever 43 in the direction indicated by the arrow 44. The reset lever 43 is suitably pivoted at 46 and thus the other end of the lever, moves in a direction indicated by the arrow 47. A heart-shaped cam 48 is carried by the pointer 33. When the end 49 of the lever 48 engages the heart-shaped cam, the cam is rotated until the corner portion 1 of the reset lever engages the notch 52 of the cam. Movement of the indicating needle is then stopped. The various parts may be so arranged that when this is done the indicating needle 33 is set to zero.

'In order to permit the resetting without stripping any of the gears or moving any of the internal parts of the indicator, the pointer 33 is frictionally carried on the shaft 32 as, for example, by a friction fit of the type indicated in FIGURE 3. Thus, the pointer 33 is carried on a cylindrical member 53 which is adapted to slide over the shaft 32 and be frictionally driven thereby. The heart-shaped cam 48 is carried by the cylindrical member and the pointer 33 may be moved with respect to the shaft 32 Without turning any of the gearing. The friction should be so selected that there is positive movement of the indicator when there is movement of the wire 18. A similar arrangement is employed for resetting the dial 36. Such an arrangement is illustrated but not described since it is identical with that described above.

In operation then, the knob 12 is unscrewed until the rod 22 is in its retracted position. The reservoir is initially filled by removing it from the apparatus, filling it, and screwing it onto the end of the barrel. The liquid is then dispensed by rotating the knob 12 to urge the rod 22 further into the reservoir 26 thereby displacing the liquid sample. To refill the reservoir after the initial filling, the end 58 of the reservoir is dipped in liquid and the knob 12 rotated in an opposite direction thereby sucking the liquid into the reservoir.

In order to eliminate backlash it is necessary to spring load the wire 18 of FIGS. 1-5. Instead of being spring loaded by the spring device 34- (see FIG. 2) the arrangement of FIG. 6 has been found very satisfactory. According to this modification, both ends of the wire or wire-like element 18 are secured to the rod or cylinder 62 as in a notch 63. The Wire 18 is passed around the cylinder 62 a number of times but an intermediate portion 18-1 of the wire 13 passes from the cylinder 62 over the pulley 60 which controls the shaft of the indicator 21 thence portion 13-2 passes directly from pulley 60 to pulley 61 and a portion 18-3 passes from pulley 61 back to the cylinder 62. Pulley 61 is rotatably mounted on a shaft 64 which is slidably mounted in a slotted opening 65 and spring pressed by spring '66 to spring load the Portions 3*; a d 1 -3 of the wire. Thus, each turn of the handle 12 of the burette winds a portion of the wire 18-3 from pulley 64 at the same time that an identical length of wire 18-1 is unwound (or vice versa). The spring pressed pulley 61 holds the wire sections 18-1, 18-2 and 18-3 tight against pulley 6i In a device of this type, it may happen that the delivery nozzle 67 of the burette will become clogged in which case forcing of the rod 22 into chamber 26 builds up great pressure within chamber 26 and tends to force liquid from said chamber back into the tube 16 which contains the measuring mechanism thus causing corrosion of the latter. The sealing means at the right of FIG. 6, shown greatly enlarged in FIG. 7, has been devised to prevent leakage of liquid from chamber 26 back into tube 16.

The tube 16 is threaded at the end 68 to retain the cap 36, and includes an internal shoulder 69 adjacent the end 68. Closely fitting the internal diameter of end 68 and resting on shoulder 69 is the sleeve 70. Sleeve 70 may be made of Teflon, Kel-F, polyethylene, polypropylene or similar inert plastic material. The inner end of sleeve 70 contains two annular recesses 71 and 72. Annular recess 71 is on the outside and is adapted to receive the O-ring '73 to seal the sleeve 76 against the end portion 68 of tube 16. Recess 72 surrounds the interior opening '74 of sleeve 76 and is adapted to receive the O-ring '75 to seal the inner end of rod 22 from chamber 26. O-rings 73 and 75 are held in place by the washer 76 which may be of metal. Washer 76 rests against the shoulder 69 of tube 16.

The inner end of chamber tube 26 is provided with an annular flange 77 adapted to be held within the fitting and its retaining ring 78 between the shoulder 79 of the ring 78 and the upper flat surface of the conical fitting 80. Ring insert 78 and conical fitting 80 may both be made of inert plastic material such as nylon, polypropylene, Teflon or Kel F. When formed of flexible plastic material, the fitting 8t) and its ring 78 may be made of one piece and the end 77 of reservoir 26 may be forced into the fitting. Once the one piece fitting and ring is assembled it cannot be distorted to permit accidental removal of the reservoir. Conical fitting 80 contains a central opening 81 to fit closely about plunger rod 22 and has a conical outer surface 82. The inclination of the conical outer surface 82 of the fitting 80 is different than the inclination of the chamfered opening 93 of the sleeve 70 so that a line contact is made between the parts '70 and 30. At least two bypassing channels 84, 85 are provided in sleeve 70 connecting the internal opening 74 of said sleeve 70 with the upper internal shoulder 86. Said ring 78 contains one or more longitudinal flat or channeled portions 88, 89'. Thus, any liquid which is forced back from chamber 26 between the rod 22 and fitting 80 finds its way into channels 84, 85, channels 88 and 89 and out through the opening in cap 30, and is thus prevented from being forced into the tube '16 because it follows the less resistant path provided by said channels 84, 35, 88 and 89, instead of the more resistant path closed by the O-ring seal 75. It will be understood that the liquid from chamber 26 is forced back to channel 84 and 88 only when pressure builds up in tube 26 through some accident such as the occurrence of an obstruction in the nozzle 67 of tube 26.

The features and principles underlying the invention described above in connection with specific exemplifications will suggest to those skilled in the art many other modifications thereof. It is accordingly desired that the appended claims shall not be limited to any specific feature or details thereof.

I claim:

1. In a liquid dispenser means comprising a reservoir and a plunger of smaller cross sectional area than the internal cross sectional area of the reservoir, the improved construction comprising;

means for operating said plunger comprising shaft means said plunger being connected axially to said shaft means at one end and having its other end free to move into said reservoir, from a first end of the latter a casing surrounding said shaft means, and extending to said first end of said reservoir,

indicator activating means connected to said shaft means and protected by said casing,

holding means for said plunger positioned at said first end of said reservoir, said holding means surrounding and slidably holding the free end of said plunger and comprising a first plunger sealing means and a second plunger sealing means,

and means in said holding means forming a lay-passing channel extending from the plunger at a region between the first and second plunger sealing means to the outside of said holding means whereby any liquid escaping from the first sealing means is by-passed to the outside and prevented from entering said casing.

2. In a burette dispenser comprising a reservoir with a small discharge opening adapted to be filled with the liquid to be dispensed, a movably mounted rod having a plunger rod extension projecting axially into the reservoir to displace liquid and force the same through said discharge opening, and mechanical means for moving said plunger rod a predetermined axial distance for each revolution of the micrometer screw;

the improvement comprising a casing surrounding said mechanical means and;

means for connecting the end of said casing to the reservoir and simultaneously sealing that end of said reservoir through which the plunger rod enters the same against leakage into said casing and the mechanical means which it surrounds;

said means for connecting the end of said casing to the reservoir comprising an internal sleeve, an interior fitting and a cap, said internal sleeve having;

a central opening for admitting the plunger rod, said central opening-being charnfered on the reservoir side thereof;

an annular recess for holding an O-ring so that the latter has the surface of its interior opening extending into contact with the plunger rod, an Q-ring fitted in said recess, and at least one by-passing channel connecting the interior central opening on the reservoir side of the annular recess to an area outside of the chamfered opening;

said interior fitting having;

a central opening for admitting said plunger rod;

an exterior frusto conical surface of a larger base but smaller slope than the chamfer of the opening in the sleeve whereby line contact is obtained between the fitting and the sleeve and whereby the fitting is spaced from the sleeve in the area above the lay-passing channel of the sleeve;

at least one of said sleeve means and said fitting including a channel connecting the area above the bypassing channel to an outer surface thereof;

said cap having a central opening to admit a part of the reservoir, and

said cap and easing comprising interfitting connections adapted to hold the parts together.

References Cited in the file of this patent UNITED STATES PATENTS 11,603,556 Platt et a1 Oct. 19, 1926 2,055,226 Zimmerman et al Sept. 22, 1936 2,952,386 Knights ept. 13, 1960 

1. IN A LIQUID DISPENSER MEANS COMPRISING A RESERVOIR AND A PLUNGER OF SMALLER CROSS SECTIONAL AREA THAN THE INTERNAL CROSS SECTIONAL AREA OF THE RESERVOIR, THE IMPROVED CONSTRUCTION COMPRISING; MEANS FOR OPERATING SAID PLUNGER COMPRISING SHAFT MEANS SAID PLUNGER BEING CONNECTED AXIALLY TO SAID SHAFT MEANS AT ONE END AND HAVING ITS OTHER END FREE TO MOVE INTO SAID RESERVOIR, FROM A FIRST END OF THE LATTER A CASING SURROUNDING SAID SHAFT MEANS, AND EXTENDING TO SAID FIRST END OF SAID RESERVOIR, INDICATOR ACTIVATING MEANS CONNECTED TO SAID SHAFT MEANS AND PROTECTED BY SAID CASING, HOLDING MEANS FOR SAID PLUNGER POSITIONED AT SAID FIRST END OF SAID RESERVOIR, SAID HOLDING MEANS SURROUNDING AND SLIDABLY HOLDING THE FREE END OF SAID PLUNGER AND COMPRISING A FIRST PLUNGER SEALING MEANS AND A SECOND PLUNGER SEALING MEANS, AND MEANS IN SAID HOLDING MEANS FORMING A BY-PASSING CHANNEL EXTENDING FROM THE PLUNGER AT A REGION BETWEEN THE FIRST AND SECOND PLUNGER SEALING MEANS TO THE OUTSIDE OF SAID HOLDING MEANS WHEREBY ANY LIQUID ESCAPING FROM THE FIRST SEALING MEANS IS BY-PASSED TO THE OUTSIDE AND PREVENTED FROM ENTERING SAID CASING. 